The overall objective of the proposed work is to establish conditions under which human tumor cells may be induced to stimulate cytolytic T-cells. A problem relevant to this objective is to understand the fundamental differences between stimulatory (S plus) and non-stimulatory (S minus) tumors, i.e., the differences between tumors which do and do not elicit a cytotoxic response directed against themselves from responding allogeneic lymphocytes. We are therefore first establishing whether a given tumor cell line is of the S plus or S minus phenotype, ascertaining whether the addition of exogenous T-cell growth factor (or interleukin 2 (IL2)) will convert S minus to S plus, and examining the relationships between tumor produced factors and IL2. In particular we will test the ability of S plus cells to enhance IL2 production, and the ability of S minus cells to act as an IL2 antagonist. In addition, we will examine, using parabiotic chambers, the proliferation of normal and leukemic lymphocytes in response to growth factors produced by normal lymphocytes and lectins when such growth factors are modified by the presence of S plus tumor cell products.